Breech-screw for ordnance.



N0. 647,380. Patented Apr. l0, I900.

A. T. DAWSON. BREECH SCREW FOR ORDNANCE.

(Application filed July 81, 1899.)

2 Sheets-$heet I.

(No Model.)

I I. I IJ I I 'll III I! ll IIIHIIHI No. 647,380. Patented Apr. I0, 1900.

A. T. DAWSON. BHEECH SCREW FDR ORDNANCE.

(Application filed July 31, 1899.)

2 SheetsSheBi 2.

II III IIIIIII: IIIIIII I I I Illllll Ill ful Improvement in in Great Britain,

NITED STATES ATENT FFIQE.

ARTHUR TREVOR DAWSON, OF LONDON, ENGLAND, ASSIGNOR TO THE VICKERS, SONS dc MAXIM, LIMITED, OF SHEFFIELD, ENGLAND.

BREECH-SCREW F OR ORDNANCE.

,SYECIFIOATION forming part of Letters Patent No. 647,380, dated April 10, 1900.

Application filed July 31', 1899. Serial No. 725,637- (No model.) 7

To all whom it may concern:

Be it known that I, ARTHUR TREVOR DAW- son,

land, have invented acertain new and use- Breech-Screws for orename, (for which I have applied for a patent dated January 3, 1899, No.

' 131,) of which the following is a specification.

' tion and to unlock it.

' the steps had the same radius.

The breech-plu g and internal screw for closing the breech of a gun are made with arcs of the thread cut away, so that it requires only a partial turn of the plug to lock it in posiextent of turn required for this purpose, and consequently the gap arcs, these arcs have been made in steps of dilferent radius, and thus there is a larger extent of thread engaged when the plug is locked in position than there'would be if all It is, however, difficult to make the screw-threads in steps, and between the stepsnotches have generally to be cut for clearance of the tool employed to cut the threads. cilitate the execution of the work, the thread instead of being made in steps has been snmetimes made as a spiral arc of radius, gradually diminishing from one end of each threaded arc to the other. This form,- which can be easily produced bya milling operation, is,

however, objectionable, because if the plug is not turned quite home the threads are not engaged to their full depth, and consequently when the threads are 'of'V-section, which is preferred for the sake of strength, the plug when not screwed fully home is in a loose shaky.condition.

My invention relates 'to the formation of the screw-thread of the breech and plug in such a way that while it can be made as easily as the spiral thread it provides against undue or objectionable. looseness and shake of the plug when it is not screwed fully home. Forthis purpose instead of making thewhole extent of the threaded are a spiral curve I make part of it of the greatest radius truly circular and concentric with the axis and the rest of it spiral, the circular portion being eased into the spiral without any abrupt break of the general curvature. This particular a citizen oi England, residing at No. 28 Victoria street, Westminster, London, Eng- In order to lessen the between the threaded In order to fa-- in each segment an arc form of thread can be easily produced by a milling operation, vand it presents the advantage that even when the plug is notscrewed quite home it is not unduly or objectionably loose or shaky, as the portions of thread'which are of circular curvature still remain engaged to'their full depth. Screws formed in the mannerdescribed may be tapered, so that the plug requires no longitudinal motion to clear the threads of the breech when it is swung in or-out on its carrier.

The accompanying drawings show breechplugs according to this invention.

Figure 1 is an end view of a plug havin'g its thread made in two segments. Fig. 2 is a side view of such plug with parallel sides. Fig. 3 is a side view of such plug made taper. Fig. 4 is an end view of a plug having its thread made in three segments. Figs. 5 and, 6 are side views showing the parallel-sided; and the taper plug, respectively. 1

Each segment of the thread consists of an arc of the largest radius from a to b truly circular and concentric with the axis of the plug, the rest of the segment from b to c bc*- ing of spiral curvature. It will be seen that; if the plug be not screwed quite home-that. is to say, if .a does not reach d, the extremity of the segment of the internal thread of the breech with which pdint a should coincide; when the plug is screwed home there is still d b circular and concentric, in which the screw-threadsare engaged to their full depth, so that the plu is '85 not unduly or objectionally-loose or shalcy.

As hereinbefore indicated, by making a breech-screwin stepped-segments of varying radius the advantage'is gained of obtaining extended length of threads in engagement; go. but the construction is disadvantageous. in that it is exceedingly diflicult to execute or manufacture. The screw with spiral segments presents the same advantage of extended lengths of screw-threads in engage.- 5 ment and the additional advantageot being convenient and easy of execution or production, but possesses the disadvantage that when not properly used-that is to say, when it is not. screwed entirely or quite home-- there is an objectionable loosenessor shake which very soon damages the screwstfhi'fifids.

' Short lengthsof concentric circular screw- This does not constantly or always occur, but occasionally does, and it is to entirely provide against this objectionable looseness or I shake that I Construct the breech-screw in segments, each having a curvature, a portion 1 which at the greatest radius is circular and of which at the greatest radius is circular and I concentric with the axis, the rest being spiral concentric with the axis, while the remaining i and eccentric with the axis, substantially as l ing the same into practical effect, I claim- A breech-screw for a mentseach having a curvature, a portion of portion is spiral and eccentric with the axis. and for the purpose set forth.

In testimony whereof Ihave hereunto set my hand in presence of two subscribing witnesses.

ARTHUR TREVOR DAWVSON.

Witnesses:

WALTER W. SHARPE, HENRY KING.

threads will not obtain the desired result in constant use. If the entire strain or explosion always comes upon them, they would shortly give way, as they become constantly weakened by constantly-repeated strains.

Having thus described the nature of this invention and the best means I know of carrygun divided into seg- 

